Heathkit Laboratory Oscilloscope IO-18 power supply question

[johnone]

Hi there!

I just bought a vintage IO-18 Heathkit Oscilloscope. Sorry for my ignorance but i would like to ask the following about its power supply: Will just an adapter make it work, or do i need to buy a power transformer and convertor as well? I know that America uses 120v ac and Greece 220/230v dc... I am a bit confused and i wouldn't want to ruin the machine, I have an adapter but i am not sure if i should just plug it in...

Thank you in advance!

[sortedradio]

Don't plug it in using just an adapter! You need a transformer to change the voltage from 220/230V ac (Greece) to 110V ac (USA)

Martin

[MrBungle]

Worth checking the insides. If Heathkit were feeling generous then there may be a dual primary transformer in there so it’ll work with a minor rewire.

[Radio Wrangler]

Heathkits were made by an American company and so you would expect them to be designed for 110v power.

BUT the heathkit company also made kits in England. These were made for 240v power and often could be set for 220 and 230v.

Did you buy this scope from America?

DO NOT connect any power until you have found out what voltage your particular scope was made for. There may be transformer tappings which can be changed. Look for any markings or labels.

It's most probable that this scope can be used only with AC power. Are you really sure that your part of Athens is on DC power?

I know it takes self control to not plug something in and try it. But it takes far more effort and money to fix something after it is destroyed, than it takes to check before the damage is done.

David

[MrBungle]

I've imported a few heathkit things and the US stuff has had dual primaries.

[mole42uk]

If it’s a UK made IO-18 it will be designated IO-18U and designed for 230/240v AC.

If it’s a USA made product it will almost certainly be 110v AC.

[Silicon]

Try to find out if the mains transformer was designed for 60Hz mains.

If it was it may overheat on 50Hz mains.

[MrBungle]

Not quite - Heathkit were pretty good with this. This is on the border line though. I think it was around the IO-18 time when they started with the beige enclosures that they shipped dual primary transformers with pretty much everything. The U just means it was UK spec which meant that Heathkit basically assembled the kit here with some local sources and modifications as that was cheaper to import. Think meters, transformers etc.

The US kits would work fine on 50Hz. I have had a US spec IB-1100, two IM-18's and a IP-2718 all from the US and they just required rewiring primaries. Never overheated, never had a problem. My father also brought a couple of their kits back from the US on a business trip around 1971 and they had dual primaries. Don't forget they shipped to South American countries as well.

Obviously don't go plugging it in to 240v without checking that out thoroughly. Looking at the internets for information, I can see that the mains lead is terminated in a tag strip and there are four wires to the transformer from the mains inlet. That might go in your favour.

[Silicon]

The 6.3V heater winding in the mains transformer can be identified by the two green wires.

If you connect the transformer to the correct mains supply you will get 6.3V AC on these wires.
If you connect the oscilloscope to a 120V step down transformer the heater voltage will be lower i.e. about 3.1V AC.

You should remove the rectifier valve before you do this test and only connect the scope to the mains for the shortest time needed to get the heater voltage.

There may be several faulty capacitors in the scope that need replacing or reforming.

Be Careful - one of the transformer windings has 1,200 V AC on it.

[MrElectronicman]

My IO-18 (USA Version) has dual primaries, that can be strapped to 120 or 240. You will need a soldering iron to make the change however.

The scope will work quite well over a range of voltages with the proper strapping